This invention relates to a fuel supplying device for an internal combustion engine having multiple cylinder.
In conventional multiple cylinder internal combustion engines, a fuel supply unit (injection valve) 1 as shown in FIG. 38 is used, in which fuel is received from a fuel pipe 2 at a top portion of the injection valve and supplied to an internal combustion engine 3 from a lower portion of the injection valve. In such a structure, however, vapor (fuel vapor) is generated when the engine is restarted in a high temperature condition, making starting impossible or causing stalling or rough idling. Further, since the fuel injection valve 1 is cooled only by a small quantity of fuel flowing therethrough, the temperature of the fuel injection valve 1 lowers little. The foregoing inconveniences last for a long time.
In view of the foregoing defects, or to quickly lower the temperature of the fuel injection valve after restarting in a high temperature condition, Japanese Utility Model Laid-Open No. 63-168, for example, has proposed to introduce fuel into the fuel injection valve through the vicinity of a side face or lower portion thereof or to cause fuel flow around the fuel injection valve by providing a holder portion in a fuel pipe. Even incorporating such measures, however, stalling or rough idling continues (for a few seconds to some tens of seconds) until the temperature of the fuel injection valve lowers down to a level where no vapor is generated.
Specifically, as shown in FIGS. 39 and 40, where the minimum distance (hereinafter referred to as the offset) L between the center of a fuel flow path defined by a fuel pipe 4 and the center of a fuel injection valve 6 provided with a holder portion 5 is "zero" or very small, since a high boiling point component (liquid) of fuel remains inside the fuel pipe 4 or fuel injection valve 6 even after a low boiling point component of fuel changes into vapor because of an increase in temperature of the fuel in the fuel pipe 4 or fuel injection valve 6, restarting is possible. However, upon actuation of a fuel pump, the high boiling point component (liquid) or fuel is pushed out of the fuel just supplied generates new vapor inside the fuel pipe 4 or fuel injection valve 6 still kept in a high temperature condition; thus, stalling or rough idling occurs. On the other hand, as shown in FIGS. 41 and 42, where the offset L is large, the residual high boiling point component (liquid) of fuel is not pushed out entirely; however, since the flow of fuel does not come into direct contact with the fuel injection valve 6, the fuel injection valve is cooled very slowly. Therefore, after the high boiling point component (liquid) of fuel is consumed, vapor is generated.